This application claims the benefit of the European Application No.: 02 026 386.9 filed Nov. 25, 2002 in the European Patent Office.
1. Field of the Invention
The invention relates to a chip-transferring station for a bonding machine, in particular a flip-chip bonder. This station is a device for picking up electronic circuits that are laid out on a carrier film and transferring them to a circuit board, in particular a ceramic substrate.
2. Description of the Related Art
In the known flip-chip method the circuits (chips) in the bonding machine are raised from the film by pins positioned below the film, and are then picked up by a suction needle, rotated through 180xc2x0, transferred to another suction needle and finally, for direct bonding, are positioned precisely relative to the circuit board by placing them on associated contact tracks. An apparatus of this kind is described in the patent JP 02 056944; see also Patent Abstracts of Japan, Vol. 014, No. 225 (E-0927) dated May 14, 1990. Another such device is known from the patent EP 1 057 388 B1.
The objective of the present invention is to make available an improved apparatus of this kind, which in particular on one hand can position the chips with high precision and on the other hand functions reliably and in such a way as not to damage the delicate chips or the contact tracks on the circuit board.
This objective is achieved by a chip-transferring station for a bonding machine with a multi-axial positioning mechanism and a suction-needle module mounted on and positionable by the positioning mechanism with a housing, a suction-needle connected to a vacuum circuit for the purpose of picking up chips and a suction-needle conveyance unit which comprises a drive motor, a belt transmission coupled thereto, and a suction-needle reversal means driven by the belt transmission, wherein the suction-needle reversal means comprises a suction-needle holder mounted on a swiveling axle and a pulley nonrotatably connected to the swiveling axle, wherein the suction-needle holder comprises a guide block on which is mounted a suction-needle carriage that can be moved only in the z direction and supports the suction-needle, and which bears a carrier bolt oriented parallel to the swiveling axle, and wherein there is nonrotatably connected to the pulley, by way of the swiveling axle, an actuator fork with which is engaged the carrier bolt extending from the suction-needle carriage and by means of which the suction-needle carriage is driven and constrained to travel exclusively in the xc2x1Z directions, wherein the guide block on the axle can be swiveled over an angular extent limited to 180xc2x0 by stopping devices, and wherein the actuator fork can swivel by more than 180xc2x0. Advantageous further developments of the idea underlying the invention of the subject matter of the dependent claims.
The proposed chip-transferring staion has a multi-axial positioning mechanism that is mounted on a base body, as well as a suction-needle module that can be positioned by the positioning mechanism and includes a (first) suction needle attached to a vacuum conduit. The positioning mechanism incorporates a suction-needle conveyance unit comprising a drive motor to which is coupled a belt, and a suction-needle reversing means driven by said belt. The reversing means comprises a suction-needle holder seated on a swivelling axle and a pulley that is fixedly connected to the swivelling axle.
The invention includes the idea of constructing the suction-needle holder asxe2x80x94in a simplified descriptionxe2x80x94a guide block with a sliding carriage that is seated on the guide block and provides the actual holder for the suction needle. In addition, the invention encompasses the idea that the suction-needle carriage is actuated by way of an actuator fork that is nonrotatably connected to the pulley by way of the swivelling axle and holds between its prongs a peg or bolt attached to the carriage. By means of the actuator fork, according to one essential aspect of the invention, the suction-needle carriage is driven and its movement restricted to the positive and negative Z directions.
Whereas the rotation of the guide block itself on the swivelling axle is limited by a stopping device to exactly 180xc2x0, and the the actuator fork can be rotated through more than 180xc2x0, the result of actuating and guiding the carriage in this way is that while the suction needle approaches and touches the chip surface, it moves along a precisely positioned vertical path. That is, relative lateral movements between suction needle and chip surface, which might otherwise occur when the chip is being picked up by the suction needle and would present a considerable risk of damage and hence wastage, are reliably prevented.
In a preferred embodiment of the invention the mounting of the suction-needle carriage in the guide block is spring-loaded, and/or the suction needle is resiliently attached to the carriage. In an even more specialized design, the suction-needle carriage is constructed as a tandem carriage, the first component of which can be moved in the Z direction within a slideway in the guide block while the second component can be moved under spring loading within a Z slideway in the first carriage component.
This use of springs in combination allows the suction needle to approach the chip surface under xe2x80x9csoftxe2x80x9d guidance, while avoiding damage to the surface by unacceptably large vertical pressures (which are the only remaining source of danger to the chip, once lateral relative movements have been excluded by the above-mentioned fork guidance).
In a first useful designxe2x80x94which from the present viewpoint is preferredxe2x80x94to implement spring-loaded guidance of the suction-needle carriage on the guide block, or of the first component of a tandem carriage, a vertical guide means is disposed in the guide block in the form of a helical spring, which acts as a compression spring between guide block and carriage. In an embodiment alternative to this, the spring tension between the two components is produced by a spiral spring associated with the swivelling axle. It should be understood that instead of steel springs, elastomer spring elements can also be used here.
In the case of the above-mentioned tandem construction of the suction-needle carriage, the spring-loaded guidance of the second carriage component with respect to the first component is preferably brought about by a traction spring disposed between the two components. In particular, again, this takes the form of a helical steel spring, but it can also be formed by an elastomer element.
In order to apply the necessary vacuum to the suction needle in a structurally simple manner, the swivelling axle is made hollow so as to form part of the vacuum conduit, and is connected to a proximal end of the suction needle by way of a flexible or rigid tube.
The above-mentioned exact delimitation of the swivelling movement of the whole suction-needle holder, in particular the carriage part, is advantageously accomplished by two stopping devices disposed on the base body of the chip-transferring station. These can, if necessary, be made adjustable, and they act on one hand to ensure that the needle moves precisely perpendicular to the chip surface during its approach, and on the other hand to establish an equally well-defined position at which the chip is transferred to the second suction needle.